Hamburgers which in their inseption were intended to provide an economical snack have gotten so big and so expensive that their operators now compete with restaurants serving full course meals.
As a result there is now a large need for a small hamburger which can be produced in large quantities to supply a substantial demand, and at a very economical pricing.
The cost of equipment to operate a hamburger sales organization has also gotten so expensive that only large well financed organizations can now enter the field. The old time "Mom and Pop" type of organization has long since been forced out of the business.